Numerous spirometer devices have been developed through the years for measuring the lung capacity of a human being. Most of these devices are fairly sophisticated and for doctors use so that an accurate measure of the lung air capacity can be determined merely by having the individual blow air from his lungs into the device after having taken a deep breath.
One drawback with most prior art spirometer devices is that they are relatively expensive to manufacture and for that reason are not generally suitable for home use by the consuming public.
Examples of prior art spirometer devices are disclosed in U.S. Pat. Nos. 3,507,271 issued to E. W. Reiner, 1,781,735 issued to R. W. Scott, 3,826,247 issued to Ruskin, et al, and 3,343,529 issued to R. A. Miller, et al.